In rolling bearing arrangements comprising angular contact bearings for the mounting of shafts in vehicle transmissions, as a rule two of the angular contact bearings are biased lash-free against each other. In angular contact rolling bearing arrangements, lash-free biasing means that the angular contact bearings are biased both in radial and in axial direction and that at least movement lashes between the rolling elements and the bearing rings within the angular contact bearings are eliminated. Angular contact bearings are taper roller bearings or angular contact roller bearings or angular contact ball bearings.
The invention relates to all types of rolling bearing arrangements with which the shafts are mounted in housings made of materials having higher thermal expansion coefficients than the mounting elements and the mounted elements. The mounting elements are the angular contact bearings. The mounted elements are the shafts, gearwheels, differential cages or planet carriers which are mounted through the rolling bearing arrangement. As a rule, the housings are made out of light metals and their alloys. The mounting and the mounted elements are made as a rule out of steel.
As known, light metals have a higher thermal expansion coefficient than steel. Due to the differences in the thermal expansion coefficients, the housing made of light metal expands more than the mounting and the mounted elements when the temperature rises. As a result, the pre-stresses in the rolling bearing arrangements can be lowered or even nullified. The reduction of pre-stresses results in axial excursion of the biased bearing rings to the point of producing lashes in the bearings with a complete absence of pre-stresses. In addition, this phenomenon known in the technical field is intensified by the fact that the bores of the mounting seats in housings made of the materials possessing the higher thermal expansion coefficients widen radially more than the respective bearing ring arranged in the bore, so that the seats of the rolling bearings in the bores can likewise loosen to the extent of giving rise to radial lashes.
Arrangements also exist in which for compensating lashes, so-called lash compensation elements are used. Through these elements which are mostly spring-elastic, the rolling bearing arrangement is retained under permanent pre-stress. Spring excursion and pre-stress are large enough to compensate expansions even in regions of the largest possible movement lashes. Such spring-elastic elements are, for example, disk springs, ondular washers or coil springs that are clamped axially between one of the axially displaceable bearing rings of one of the angular contact bearings and an axial support fixed on a surrounding part.
As also described in U.S. Pat. No. 5,028,152 A, thermo compensation elements, also called TCE's are used in such rolling bearing arrangements. These TCE's are made of a material whose thermal expansion coefficient, as a rule, is much higher than that of the housing. The TCE's are seated on the outer periphery of the respective axially displaceable bearing ring and protrude in axial direction beyond the axially directed front end of the outer ring while being biased against an axial housing-mounted stop. Upon a rise of temperature in the surroundings of the rolling bearing arrangement, the TCE's, due to their higher thermal expansion coefficients, expand more than the housing, so that the axially protruding portion of the TCE lengthens in axial direction and the pre-stress in the rolling bearing arrangement is maintained. Because compared to steel and also to light metals, the TCE's are made of a relatively soft material they are encapsulated at least partially by a U-shaped ring profile. The ring profile is given the shape of the TCE's, and retains them in position while protecting them through axial stops in the contact zone particularly in the contact with the housing.
The housing described in U.S. Pat. No. 5,028,152 A is a ring profile that, in longitudinal section, is configured with a U-shape longitudinally along the central axis of the ring profile or along the central axis of the respective angular contact bearing. Viewed in any longitudinal section, the two legs of the U-profile are radially parallel to each other and are oriented in axial direction axially parallel to the central axis. The web that connects the legs is oriented in radial direction and thus crosswise to the central axis. The TCE is supported axially on the housing through the web.
In the rolling bearing arrangement described in U.S. Pat. No. 5,028,152 A, the bearing ring on which the TCE is seated must comprise a valley channel for this seat. By valley channel is to be understood a region on which two surfaces converge and form an inner corner. The surfaces in the present case are a circular ring surface and an outer cylindrical surface. The valley channel must possess axial and radial dimensions that correspond substantially to the dimensions of the TCE. Such a valley channel can be made in a bearing ring only if the bearing ring has adequate axial and radial dimensions: if not, the bearing capacity of the bearing ring is deteriorated because an insufficient quantity of material remains behind in the regions next to the raceways of the rolling elements for supporting the rolling contact of the rolling elements with the raceways. Frequently, the axial and the radial design space available for the accommodation of the angular contact bearing is tightly designed so that the dimensions of the bearing ring have no place for such valley channels. Moreover, for being able to receive the TCE's, the bearing rings must have generous radial and axial dimensions, and this has a detrimental effect on their material requirement and their weight.